This invention relates to civil engineering, in particular to a culvert built as a crossing or driveway especially in the road ditches that drain water from roads. The subject of the invention is a culvert of increased safety fitted with deformation zone that limits the risk of fatal consequences of accidents when a car goes off the road and hits the culvert.
In most cases, the culverts are constructed as solid structures with vertical fronts. A tube for conducting water through the culvert is installed in a concrete bed and concreted and backfilled between solid, usually concrete or bricked, fronts. The main disadvantage of this solution, particularly with respect to safety, is the vertical front of the culvert because consequences of frontal crash of a car slipping from the road hitting the vertical culvert front are usually serious and result in fatal car accidents. The other disadvantage is the wet process of construction of the fronts lengthening the construction time and does not allow construction works at low temperatures.
The culvert with inclined front is another option of the solution. It eliminates the danger of frontal crash for a car going off the road. On the other hand it happens that the car rides on the culvert at high speed and is catapulted back to the road with identically serious, if not much more serious, consequences than the frontal crash with the vertical culvert front. In addition, construction of the inclined front is technologically much more demanding and appropriate cutting of the tube is required and therefore, construction of the culvert is more expensive and time demanding compared to the vertical front culvert, including the disadvantage of the wet process.
The utility design CZ 19993 describes a solution that should minimize fatal consequences of the frontal crash of a car in the culvert front. The design of the culvert contains a deformation zone consisting of the “U” shaped piece filled with two opposite concrete deformation fronts with stiff, non-deformable bumpers and opposite blocs. Front pieces, sliding in the basic shaped piece, are adjacent to both fronts. The basic shaped piece with the front covers a decking consisting of sliding telescopic segments. The decking is covered with gravel for vehicles to pass. Upon impact, the front pieces retract and activate the protective functions of the deformation front and the bloc. After accident, the front piece is removed and the damaged deformation fronts with the blocs are either extracted or removed after removal of the backfill and the decking. Serious consequences of the frontal impact are thus really minimized but on the other hand, construction, building and maintenance of the culvert is demanding. The basic “U” shaped piece does not follow the ditch shape, which is usually in “V” shape and ground works must always be performed to install the shaped piece in the ditch. The solution is extensive and heavy, which increases both production as well as transport costs related to prefabricated components.
The utility model CZ 19993 describes also an option of the culvert applicable as crossing for bike riders or pedestrians over the road ditch. This option of the culvert is constructed without the base shaped piece. It only consists of deformation fronts with the deformation bloc that may be installed between them. The fronts are covered by a decking with backfill. This solution is not suitable for driveways of cars because of limited loading capacity.
The task of the invention is to create a culvert with improved safety diminishing the danger for cars going off the road, the construction costs of which would be low, not time demanding; the culvert requiring minimum maintenance and in case of damage it would require minimal reparations.
The above specified goal is achieved by creation of a culvert according to this invention. The culvert with the deformation zone consists of prefabricated components installed in the road ditch with at least one fixed basic component and one deformation sliding component in the basic component in the direction of longitudinal ditch axis. The culvert assembly is covered by a deformable decking or backfill or otherwise.
The substance of the culvert according to this invention lies in the fact that the basic component consists of a set of prefabricated concrete or reinforced concrete beds of a “V” shape placed one after another in the concrete foundation in the road ditch so that the bed shoulders abut the ditch walls. Both shoulders of each bed are fitted with opposite guiding recess for installation of the deformation components consisting of an assembly of at least two lateral stiff girders installed with the possibility of a sliding movement in the direction of the longitudinal ditch axis. There are deformation gaps between the lateral rigid girders and at least one culvert front recess with possibility of the sliding movement of at least one further deformation component that forms the front component provided with soft layer made of deformable and tough material at least on its front side.
The advantage of this design of the culvert is that it does not contain any large basic “U” shaped piece that would increase the construction costs and the “V” shaped beds follow the ditch shape and therefore, the ground works are limited to a necessary minimum consisting of landscaping to install the concrete foundation and the beds. The deformation zone directly consists of lateral stiff girders included in the decking and their sliding is easily ensured by dry placement in the beds, allowing them to slide in the deformation gaps, which allows for deformability of the culvert in the longitudinal direction together with the front component or components. The front component made of soft and tough deformable material absorbs a part of kinetic energy of a car during impact by means of its own deformation and therefore, at lower speeds, the lateral rigid girders may not slide at all. The front component also ensures even sliding of the lateral rigid girders at impacts of higher kinetic energy. Warning road safety equipment of deformable design can be installed on the front component, e.g. direction columns or road fences. In case of higher impact speeds, e.g. in rural zones, the culvert can be fitted with any number of deformable front components arranged in a row.
In an advantageous embodiment of the invention the bed of the culvert forms two independent shoulders placed on a foot fitted with retaining slants and connected with the bottom. In this embodiment, the prefabricated components prepared to be assembled are light and storable and therefore, they are suitable for manual handling during transport and assembly.
In another advantageous embodiment of the culvert the guiding recesses in the bed shoulders of the culvert are created as “L” shaped open semi-grooves and the lateral rigid girders are on both ends adjusted in the shape of flat profile fitting in the guiding recess.
The lateral rigid girders may be made of concrete, reinforced concrete, wood or a composite plastic material. The beds are made of concrete or reinforced concrete. To secure the sliding movement of the girders in the recesses of the bed shoulders, their plain dry fitting is sufficient or a sliding Teflon layer may be installed here.
In another advantageous embodiment of the culvert the lower part of the lateral rigid girders are provided with the guiding and supporting brackets fitted on the bed shoulders.
The shape of the girders is designed so that the girders show sufficient vertical rigidity and strength at low weight and the girders do not collapse inside the bed or lift above the upper edge of the culver in case of crash. To this the advantageous embodiment of the girder corresponds where the upper girder part consists of two flat shoulders and the guiding and supporting brackets are directed in the normal line direction to the bed shoulder surfaces.
In another advantageous embodiment of the culvert the deformable decking designed so that the deformation gaps between individual lateral rigid girders are covered by flexible strips that form the decking of the culvert with the upper sides of the girders.
The flexible strips must be of sufficient loading capacity so that they can be backfilled or covered. They also must be easily deformable to ensure good deformability of the culvert in longitudinal direction together with the sliding movement of the girders and the function of the front components. The advantage of the flexible strips consists in their easy replacement during reparation of the deformed culvert which will be damaged only partially in most cases. The benefits of the rubber strips consist in improved draining of the road on the driveway point.
The flexible strips are advantageously made of rubber and fitted with reinforcing and distance ribs on their lower side to fit in the deformation gaps.
During assembly, the ribbed rubber strips will also provide technological spacing of the lateral rigid girders for creation of the deformation gaps. On the culvert decking, there is backfilling, preferably from light aggregate for easy movement of the girders in longitudinal direction. The backfilling may be made of e.g. soil, gravel or as a cover of bitumen road or otherwise. Depending on growing load of the decking and deteriorated conditions for shifting of the girders, the culvert may be fitted with higher number of deformable front components.
In another advantageous embodiment of the culvert the inner components of the bed bottom are rounded, arranged at the same level as the ditch bottom and the assembly of beds in the road ditch exceeds the assembly of lateral rigid girders and front components in the direction of longitudinal axis of the road ditch at least on one side of the culvert. In this embodiment, the culver fully follows the shape and profile of the road ditch and in case of the beds exceeding the assembly on both sides, the culvert can slide in both directions in the longitudinal axis of the ditch in case of impact.
It is furthermore advantageous that the front component in the vertical direction exceeds in height the upper edges of the bed shoulders over the upper edges of the lateral rigid girders or over the upper edges of the strips. In this embodiment, the front component sweeps the flexible strips during the impact to avoid their contact with a car crashed and forms a border for application of the backfilling or bitumen or other road surface of the driveway.
It is furthermore advantageous when the front component forms a sandwich panel with alternate soft polyurethane layers, air layers and fixed layers made of solid plastic ribs for spatial rigidity in two directions, whereas the road-fence and/or warning column is preferably anchored to the front component.
It is finally advantageous when draining holes are made on the bed shoulders for draining water from side walls of the ditch in the culvert.
The advantages of the culvert according to the invention consist in that the double deformation zone significantly reduces the overload value applicable on the car crew at the moment of impact and in consequence of which traumatic injuries occur. Thanks to simple composition of the prefabricated components, the culvert is characteristic by a short construction time, for a standard culvert the construction time is about 2 days. Another benefit is an easy maintenance because the culvert has higher bore diameter compared to classic construction procedure; if the culvert is highly contaminated (e.g. by sludge), the culvert can be disassembled easily and reassembled after cleaning and when the culvert is damaged by an impact, only damaged part need be replaced.
Furthermore, the culvert is characteristic by high durability due to improved quality of prefabricated components and lower price due to series production of the prefabricated components as well as easy construction without use of heavy machinery.
Finally, better draining is advantageous because the culvert does not interrupt draining of the ground plane and improves better road draining along the culver in case of rubber road surface.